1. Field of the Invention
The present invention relates to semiconductor manufacturing, and in particular to a method of avoiding CMP caused residue on wafer edge uncompleted field.
2. Description of the Prior Art
Manufacturing of semiconductor substrates encompasses hundreds of different process steps. The steps involve creating patterns, introducing dopants, and depositing films on a silicon substrate repetitively throughout the manufacturing process to form integrated structures. Because the various structures that are built on a substrate or a wafer are serial in nature, that is, that they are built one on top of another in a sequential manner, it becomes very important that each layer of structure is substantially defect free before the next one is placed thereon.
Defects are generally caused when an unwanted particulate matter unintentionally lands between features on a layer and "bridges" or connects them, and therefore, disables them by "shorting" under certain conditions; or when an unwanted particulate matter lands on a feature, and disables it by creating an unwanted "open" in the circuitry. The size of the particulates in relation to the size of the features play an important role in creating the defects. As the size of features in today's high density integrated circuit chips (IC) are getting miniaturized ever so incessantly, control over the size of contaminants introduced into the manufacturing line need also be scrutinized diligently if acceptable levels of yield are to be maintained. Thus, for submicron lithographic technologies where the wiring features or patterns are less than one micrometer, .mu., in width, the size of the invading particulate matter need be controlled to between about one fifth to one tenth of the width, or between about 0.1-0.25.mu.. With chip sites of about 5 mm.times.5 mm on a wafer, or of an area of 25 mm.sup.2, the allowable defect density is about 0.02 pieces/mm.sup.2 in order to achieve satisfactory levels of yield. For larger chip areas on the order of 100 mm.sup.2, the defect density must be below 0.003 pieces/mm.sup.2 in order to achieve the same yield.
Defects can best be avoided if the sources of the contaminants or dust particles are eliminated. There are mainly two major sources for contaminants that are introduced into a manufacturing line: the first one is that which resides outside the work piece, namely the wafer, such as the ambient air surrounding the wafer, or fluids, such as chemicals, that are brought to the work piece for various processes that take place at the work-station. These contaminants that are external to the work piece and sometimes are known as "drop-ons", can generally be kept away from the work-piece by proper use of filters, and other implements that are commonly available. The other source for particle contaminants is the work piece itself, and the contaminants generated from the work-piece is sometimes referred to as being "process-induced." As work is being performed on the work-piece, the work-piece releases particulate matter, or dust, due to abrasion or breakage caused by excessive stresses imposed on certain parts of the work-piece. Further on, the uncompleted fields of wafer edge with higher altitude will cause a lot of particulate matter after chemical mechanical polishing (CMP).
A case in point is when a wafer, for example, has ups and downs topography. As expected, defect particles will stay in fovea region and near uncompleted field of wafer edge to kill yield. Moreover, topography will cause photo-defocus issue at the following layers.